I have a problem with RFI (radio frequency interference) that is disrupting the proper operation of a level control system for a public water supply. I am trying to find someone who has access to a radio signal analyzer or spectrum analyzer to troubleshoot the problem. It is at a relatively low frequency, 27 mHz. (CB radio frequency range). Does anyone on here know of a company or person who is working in the field of emergency radio communications (police, fire, ambulance). If not, any retired ham radio buffs on here who might have a Spec. A?

My analog carrier is FM at 26.995 mHz but the receiver is getting "swamped" with so much RFI I am unable to capture the trigger pulses (simple digital FSK) sent by the transmitter to turn on my system. The frequency on this system is fixed so I can't move to another channel. My hope is to find someone with a coms analyzer and directional antenna and isolate the source. I "suspect" there is a problem with the local municipality's police radio system but I'm going to have to prove it to them to get them to do anything about it.

Yes, agree.. spectrum analyzer would allow a view of occupied bandwidth on and around your 26.995Mhz carrier. Need to determine if other transmissions are on channel or adjacent channel and how much energy. Is this "interference" full time ? A sharp bandpass filter on receiver tuned on center freq. might resolve but probably not easy to add. Is jumping to another operating frequency possible ? I think locating a 2way shop in area is good idea.

Thanks four your response Woody. The interference is not full time and seems to last for a few hours one or two times a week. In my mind this rules out the possibility of spurious EMI from electrical equipment in the immediate vicinity. There is a Telcel tower close by to the site but those frequencies and associated harmonics should be way higher in spectrum. I suspect somebody may be operating a "CB" radio like device with illegal RF power amp but have not yet located any antennas around that might tip them off. There is a police radio site apparently in a village nearby (within about 1km.) but I think Mexico uses the same bands as the rest of North America - 150 mHz.

I can't alter the frequency as far as I know but have emailed the radio mfg. (Remote Control Technologies) to see if they have any suggestions. KR have some nice 50 ohm bandpass filters like the KR2473-B so maybe I'll need to get a couple of those for my antenna feeds.

For now, I have sourced another receiver to set up in my vehicle and as soon as I find a suitable antenna I'll start driving around and see if I can narrow down the source of the noise. Mexico also has an equivalent of the FCC but not sure how to open a complaint yet.

Just to close this off, I think the problem has been resolved. I was unable to find anyone who could do a site survey or find a spectrum analyzer so I rigged up a spare receiver and antenna in my truck and drove all over the area. It quickly became apparent that the RFI was radiating off the CFE power lines in one branch of their high voltage feed along the road adjacent to my installation and through the nearby village. The only heavy power user along this branch is a bakery which led me to suspect that there was a problem with a piece of equipment in the bakery such as an oven. The bakery closed up shop at the end of December and moved and I have had no interference problems since. Just to be safe I also obtained a couple of bandpass filters (Mini-Circuits BBP-21.4+) and installed them on my receivers so I think the problem is now resolved.

Ezzie, Glad to see that interference has settled down. You must have solid background in communications. I'm retiring this May 1st after working in radio/tv engineering field in US.. We have family living in Joco for many years. Looking forward to spending a lot more time lakeside. Hope to meet you down the road. Cheers !

I am still seeing RFI coming off the CFE lines on a sporadic basis. I've tried bandpass filters on the receivers but it still gets through. I think the only solution is going to be to move my antenna further away from the power lines and switch the control system over to solar power (DC). I don't think CFE uses any capacitors on any of their primary feeds and their grounding systems are somewhat questionable.

Ezzie wrote:I am still seeing RFI coming off the CFE lines on a sporadic basis. I've tried bandpass filters on the receivers but it still gets through. I think the only solution is going to be to move my antenna further away from the power lines and switch the control system over to solar power (DC). I don't think CFE uses any capacitors on any of their primary feeds and their grounding systems are somewhat questionable.